A 1223g sample of solid containing ascorbic acid and inert...

A 1.223g sample of solid containing ascorbic acid and inert ingredients was dissolved in dilute H 22 SO 44 and treated with 2 g of KI and 50 mL of KIO 33 solution from part (a). Excess triiodide required 14.22mL of Na 22 S 22 O 33 solution from part (b). Find the weight percent of ascorbic acid (FW 176.13) in the unknown.

The amount of ascorbic acid (FM 176.12) in a sample can be determined by iodometric titration. A 10.00-mL aliquot of a solution with an unknown ascorbic acid concentration was first pipetted into an Erlenmeyer flask, along with 5 mL of 5% KI solution and 1.5 mL of 6 M H2SO4. The mixture was then titrated rapidly with 1.897 mM KIO3 solution while swirling the flask between additions, until the yellow color of the I3- complex almost persisted. Then four drops of starch indicator were added and the titration continued until the blue color of the starch-iodine complex persisted. The total amount of KIO3 solution used was 38.72 mL. Report the ascorbic acid concentration in mg ascorbic acid/100 mL solution. IO3- + 8 I- + 6 H+ ⇌ 3 I3- + 3H2O C6H8O6 + I3- ⇌ C6H6O6 + 3 I- + 2 H+

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